The complete and assured sanitization, detoxification, disinfection, high-level disinfection, or sterilization of devices, tools and other objects in industries such as but not limited to the health care industry, has always been a challenge in terms of processing time, cost, engineering tradeoffs, toxicity, safety, and overall effectiveness. Currently, the available choices are liquid disinfection, typically referred to as a “wet” method, and various airborne methods, typically referred to as a “dry” method. The dry method can include, but is not limited to, gases, aerosols, and processes that use steam as a carrier gas for the disinfecting composition or solution. All processes that do not include liquid immersion are generally considered to constitute a dry method even if the agent used has a liquid phase.
Immersion of an object in liquids known in the art for sterilization or disinfection is a relatively simple method that is cost effective, and offers fast cycle times that are typically measured in hours. However, it also presents problems related to reproducibility and quality assurance due to the potential for bubbles to form on the inner surfaces of complex instruments, including endoscopes, which prevent cleaning solution contact with interior surfaces, such as lumens or channels. Another method for cleaning devices such as endoscopes is known to those skilled in the art, but generally involves several sequential steps or activities such as, but not limited to, wiping the scope off to remove any unwanted debris or contaminants and then placing the endoscope in a washer and interfacing it with a hose, or other means known to those skilled in the art (herein called “supply tube”). The supply tube enables various liquids including but not limited to, surfactant, high purity rinse water, and disinfectant/sterilant, to be moved through the various channels and lumens of the endoscope at various stages of the cleaning process. The outside of the endoscope is also exposed, preferably simultaneously, to these same liquids at various stages of the cleaning process. After the final rinse stage, the endoscope is dried in a manner known to those skilled in the art including, but not limited to, being dried within the processing chamber, or removed from the washer and dried outside of the processing chamber.
The current art can be improved in various ways including, but not limited to: (1) decreasing the time required to achieve the desired anti-pathogen/toxin/fungal/sporicidal effect on both the internal and external surfaces as well as any interfacing/articulating surfaces of an object or endoscope (2) reducing the risk that “air bubbles” will prevent full contact of the disinfectant/sterilant solution with all inner surfaces of an object or endoscope (3) reducing the drying time for an object or endoscope, and (4) reducing or eliminating the deleterious effect of the disinfectant solution and/or disinfecting process on the materials that are used to construct the object or endoscope. The methods and apparatuses of the present invention address these needs by decreasing the time to efficaciously complete the essential steps while achieving a satisfactory result.
In general, liquid disinfection/sterilization creates a major corresponding drawback in that the finished product remains wet, and therefore unsuitable for packaging and/or storage. The deployed or applied disinfecting agent(s) or substance(s) must have limited toxicity, be reasonably safe as well as compatible with those materials comprising the instruments and devices to be disinfected/sterilized.
Gaseous agents used in the prior art for sterilization are very limited in terms of medical applicability. Steam or dry heat sterilization is effective, but many medical devices and instruments are incompatible with the degree of heat required for this process. So-called “cold sterilization” is an alternative, but the only currently available cold sterilization agents in use in hospitals are ethylene oxide and hydrogen peroxide in various forms that include, but are not limited to plasma. U.S. Pat. No. 4,512,951 (Koubek, 1983), which is incorporated herein by reference in its entirety, including any references cited therein, teaches using hydrogen peroxide to sterilize medical articles by causing hydrogen peroxide-water vapors to deposit a film of liquid on the medical devices. The liquid film is then caused to be evaporated. Hydrogen peroxide vapor is susceptible to humidity that can reduce the efficacy of the process.
Ethylene oxide (EtO) is carcinogenic, toxic and dangerous and, although effective, is only used as a last resort for instruments and devices that cannot be subjected to other modalities. In addition, after being exposed to EtO, items cannot be used for long periods to allow “off-gassing” or aeration of the EtO. According to the UNC School of Dentistry, the complete EtO cycle, including aeration, can last as long as 24 hours. The newer technology utilizing hydrogen peroxide plasma is an alternative, however, it is very expensive, and the technology requirements have translated to only small size sterilization chambers. To date, it has not been capable of sterilizing certain instruments including, but not limited to, endoscopes. Endoscopes generally contain small lumens and/or channels and the hydrogen peroxide plasma has difficulty in maintaining its effectiveness throughout the length of the lumen.
Without being limited to a mechanism, method, or chemical, it is believed that chemically reactive liquids are necessary in sterilization processes to contact contaminants including but not limited to toxins, bacteria, virus, fungus, and spores (both fungal and bacterial), prions or protein structures, within a target area(s) to either kill or neutralize the bacteria, virus, fungus, and spores, or to render the toxin, virus, or protein structure incapable of replication or to otherwise interfere with the target's cellular physiology, or to destroy or neutralize the toxin. These chemically reactive liquids may be provided as an aerosol.
Prior art has taught that relatively quick disinfection and sterilization of objects can be achieved by their exposure to an aerosol of a disinfectant/sterilizing agent created by ultrasonic nebulization. U.S. Pat. No. 4,366,125 (Kodera et al., 1980), which is incorporated herein by reference in its entirety, including any references cited therein, teaches that an aerosol, created by ultrasonic transducers and consisting of hydrogen peroxide, can contact surfaces targeted for sterilization. Ultraviolet-ray lamps are then synergistically used in concert with the applied aerosol to achieve sterilization of the targeted surfaces. Generally, the prior art also describes apparatuses and methods where the aerosol is generated by one or more ultrasonic transducers located below the surface of a reservoir containing a liquid. The output of the transducers is focused to either a point and/or directed toward an area near the surface of the liquid to cause a surface disturbance, which results in the formation of an aerosol from the liquid. The transducers used in these apparatuses are typically made from lead-zirconate-titanate-four (PZT-4) or other piezoelectric materials. This material is coated with a conductive coating (i.e., an electrode material) that enables an electrical signal to energize the transducer and causes it to emit high frequency pressure (energy).
G.B. Patent No. 1,128,245, (Rosdahl et al., 1968) which is incorporated herein by reference in its entirety, including any references cited therein, describes a device for disinfecting apparatuses and instruments, including medical instruments. This apparatus also generates a mist of disinfectant, including hydrogen peroxide, by means of an ultrasonic aerosol generator. According to Rosdahl et al., this patent was “primarily adapted for the disinfection of small medical instruments such as scalpels, tongs, syringes, or the like, positioned on a grid in a container” (pg 3 col. 23-30). However, another separate intended use for a second described apparatus was for disinfecting interior surfaces of objects such as the interior of tubing used for “breathing apparatuses” and “heart lung machines” (pg 1 ln 30-36 and pg 2 ln 95-101).
Rosdahl et al. is distinguished from the present invention in that it is silent with respect to simultaneously disinfecting both the interior and exterior surfaces of an object. Rosdahl et al. also does not teach a method for simultaneously sterilizing/disinfecting and drying the outside and interior surfaces/lumen of an object. Most importantly, Rosdahl et al. does not teach how the apparatus could effectively and efficaciously be “connected” to the object (pg 2 ln 95-101) in a way that enables all of the interfaced/articulated surfaces to be sanitized, disinfected, high level disinfected, or sterilized. The pressurized air in Rosdahl et al. is supplied by way of a fan etc. or carrier gas, (pg 2 ln 48-49) and is used to both move the generated aerosol to perform the disinfection function, and to dry the objects placed within the enclosed area of their described apparatus after disinfection. Rosdahl et al. incorporated “a heating element in the flow path of the carrier gas, to increase drying efficiency” (pg 3 ln. 123-127) by heating the air. The use of a heating element in the flow path of a gas stream taught in U.S. Pat. No. 6,379,616 (Sheiman, 1999), is incorporated herein by reference in its entirety, including any references cited therein. Sheiman also teaches the use of ultrasonic transducers to generate aerosol. The heater is located about the inlet conduit of the apparatus and is designed to heat the aerosol, which encourages its condensation on or within the article. It is important to note that Sheiman is silent regarding the use of the apparatus or a secondary apparatus to interface and sanitize, disinfect, high-level disinfect, or sterilize, the interior of an object or device, as well as the simultaneous or non-simultaneous cleaning of both the interior and exterior of objects.
Ultrasonic nebulizers have a unique advantage in that they can create small aerosol droplets less than 5 microns in size. The size of the droplets enables them to penetrate small cracks and crevices and to behave like a gas due to Brownian movement and diffusion. In addition, the cloud is able to form a very thin coating, deposition, or film over various surfaces that is inherent to this technology and method. The thin coating, film, or deposition of sterilant or disinfectant is able to dry much faster than coatings created by aerosol containing droplets that are much larger in diameter. It is also theorized that the vapor component contributed by the evaporation of the generated droplets, or even partial touching of the aerosol droplets with the targeted contaminant(s) can contribute to the overall efficacy of the process.                U.S. Pat. No. 4,366,125, (Kodera et al., 1980), which is incorporated herein by reference in its entirety, including any references cited therein, teaches that heated H2O2 was more efficacious than H2O2 used at room temperature (col. 1, line 19-25). In other words, (Kodera et al., 1980) teaches that the efficacious nature of a liquid agent can be increased as it is heated to temperatures higher than ambient temperature. This is desired, without limitation, in the present invention. The text entitled, “Aerosol Technology” by William C. Hinds (1982), which is incorporated herein by reference in its entirety, including any references cited therein, also taught that the size of the aerosol particles produced by ultrasonic means are not only affected by the frequency of the transducer operation, but also by the surface tension and density of the liquid.        
It is commonly known that heating a liquid to a temperature less than its boiling point will reduce its surface tension. William C. Hinds (1982) established that the higher the temperature of the liquid, the lower the liquid's surface tension, resulting in smaller sized aerosol particles. This principal is incorporated without limitation, in the present invention. In the same text he also taught that smaller diameter particles demonstrate characteristics such as but not limited to, a lower settling velocity, a higher diffusion coefficient, and a higher Brownian displacement (movement), which is desired, without limitation, in the present invention. Hinds further taught that ultrasonic aerosol generating transducers can heat the surrounding liquid (page 382). This is also desired, without limitation, in the present invention.
Despite the advantages that ultrasonic nebulization offers, currently it has major limitations in its usefulness and has not been successful in meeting the needs of medical sterilization. For example, and without limitation, it is difficult and time consuming with the prior art devices and methods to disinfect or sterilize both the exterior and interior surfaces of tools or equipment, e.g., endoscopes, in a single cleaning cycle or process due to their complex construction including narrow lumens of various length. The limitations of the prior art are further indicated by the failure or problems which various anti-pathogen/toxin/fungal/sporicidal agents or substances have in contacting, and/or rapidly achieving an efficacious result on, the surfaces of the endoscope or object that are interfaced/articulated with any coupling(s) or other device.
“Flash” sterilization is also needed in industries such as, but not limited to the health care industry. It is commonly used for quick sterilization and turn around of various objects immediately needed for or during surgery. Flash sterilization methods that include the use of steam under pressure at recommended temperatures of approximately 270 degree Fahrenheit for approximately three to ten (3 to 10) minutes, are generally representative of the current art. The object that is flash sterilized must then cool down before it is used, which also takes valuable time. A need still exists in the industry to further reduce the total amount of time it takes to clean, sterilize or disinfect, and deliver a surgical tool on demand within a reasonable period of time. The present invention can, without limitation, decrease the total cycle time needed for rapid sterilization of medical devices by providing a means to quickly sterilize or disinfect objects whose construction materials are thermally sensitive and cannot be flash sterilized by current means.
The methods and apparatuses of the present invention address the need for a quick and effective way to fully sanitize, detoxify, disinfect, high level disinfect, or sterilize both the interior and exterior of medical devices, and objects. In addition, this may without limitation, be accomplished while still enabling all surfaces of the object or endoscope to have contact with the anti-pathogen/toxin/fungal/sporicidal agent(s) or substance(s) including surfaces of the object or endoscope that are interfaced/articulated with any coupling(s) or other device.